Electronic musical instrument with automatic rhythm section triggered by organ section play

ABSTRACT

An electronic musical instrument comprises an organ section including playing keys and an automatic rhythm playing section including a clock pulse oscillator, counter stages, a rhythm pattern pulse encoder, rhythm selector switches, rhythm tone generators, a key depression detector, a rhythm cycle end detector, and a start-stop control. When keys are depressed on the first beat in every measure, a trigger signal is produced from the key depression detector and fed to the start-stop control, thereby initiating the automatic rhythm performance. When the automatic performance comes to the end of its rhythm cycle, another trigger signal is produced from the rhythm cycle end detector and fed to the start-stop control, thereby terminating the automatic rhythm performance. The rhythm section plays automatic rhythm performance cycle by cycle upon key depression in the organ section. The automatic rhythm performance will thus be in better accord with the organ section playing tempo.

Okamoto ELECTRONIC MUSICAL INSTRUMENT WITH AUTOMATIC RHYTHM SECTIONTRIGGERED BY ORGAN SECTION PLAY [111 3,840,691 [451 Oct. 8, 1974 PrimaryExaminer-Richard B. Wilkinson Assistant ExaminerU. Weldon Attorney,Agent, or Firm-Flynn & Frishauf [75] Inventor: Shimaji Okamoto,Hamamatsu,

Japan 57] ABSTRACT Assigneei lf l Sello Kabushiki An electronic musicalinstrument comprises an organ Kalsha, Shlzuoka-ken, Japan sectionincluding. playing keys and an automatic [22] Filed: Oct 11, 1972 rhythmplaying section including a clock pulse oscillator, counter stages, arhythm pattern pulse encoder, PP 296,599 rhythm selector switches,rhythm tone generators, at key depression detector, a rhythm cycle enddetector, [30] Foreign Application priority Data and a start-stopcontrol. When keys are depressed on O t 18 1971 J 46 82353 the firstbeat in every measure, a trigger signal is proc apan duced from the keydepression detector and fed to the start-stop control, therebyinitiating the automatic F;tS.(l. performancew the automatic p ancecomesto the end of its rhythm cycle, another [58] Field of Search 84/ L01,1.03, 1.24, DIG. l2 trigger Signal is produced from the rhythm cycle enddetectorand fed to the start-stop control, thereby ter- [56] ReferencesC'ted minating the automatic rhythm performance. The UNITED STATESPATENTS rhythm section plays automatic rhythm performance 3,478,633ll/l969 Mallett 84/].03 cycle by cycle upon key depression in the organsec- 3,548,066 12/1970 Freeman 84/l.03 tion The automaticrhythmperformance will thus be in better accord with the organ section playingtempo. l w 3,712,950 1/1973 Freeman 84/103 1 Claims, 6 ing igu es 27 vCYCLE END J DETECTOR 12 10 -2 32 i3 25 Q 13, 15, r3 e 1 START- KEYR'ESET STOP STAGE STAGE STAGE STAGE DEPRESSION I CONTROL 29 LATOR r 2 34 DETECTOR SET ClRCUIT I E I I i l l L" i5 3 -24 I l ..3 issl. I A R 1 ll V M l 52 l RESET- RHYTHM R2 i? T t l T l l l l r i T I 22 3 E 'QS l ISELECTlON R s, l l 5h Ll I1 CIRCUIT HE SPPQ e a nn [r1111 PAIENIEHHCI3.840.691

SHEET 30$ 4 FIG?) TO START- TO FIRST COUNTER STOP CONTROL STAGE CIRCUIT2+ w FROM CLOCK W 83%? zsua T fi RwE COUNTER STAGE 42 OR RHYTHM CYCLER14 END DETECTOR 51 TO RESETTING r 7 m CIRCUIT TO RHYTHM PATTERN PULSEENCODER TO COUNTERS ELECTRONIC MUSICAL INSTRUMENT WITH AUTOMATIC RHYTHMSECTION TRIGGERED BY ORGAN SECTION PLAY This invention relates to anelectronic musical instrument such as an electronic organ and moreparticularly to a type provided not only with an inherent organ sectionbut also with an automatic rhythm section.

Automatic rhythm instruments heretofore put to practical applicationgenerally include a clock pulse oscillator adapted to generate arepetitive basic tempo pulse train having a frequency or time widthcorresponding to the shortest beat unit (e.g. a quaver or semiquaver) ofthe rhythm performance and followed by a multistage frequency dividingcounter chain. Output pulses from the respective stages of the counterchain are introduced into a rhythm pattern pulse encoder constructed ofthe known diode matrix circuit to be converted into various sets ofrequired rhythm pattern pulses'for march, rumba, tango, and so forth.

Before the start or initiation of a rhythm performance, a player selectsthe desired one or more of various rhythm tempos. Under thisarrangement, sounds like those of Various percussion instruments such ascymbals, maracas, claves or ordinary chord or bass sounds orcombinations thereof are automatically produced in accordance with thepreselected rhythm pattern pulses.- I

Where, however, such automatic rhythm instrument is incorporated inkeyboard electronic musical instruments such as an electronic organ, therhythm sound performance goesautomatically by itself and independentlyof the organ section performance and then the organ section forproducing ordinary melody sounds or accompaniment sounds like those ofthe chord or bass upon selective depression of the manual and/or pedalkeys of the instrument has to be so played as to meet the tempo of theautomatic performance of the rhythm section.

Accordingly, it is very difficult for player other than those having anadvanced skill to attain a performance on the organ section at a tempoperfectly. in conformity to the tempoof the automatically producedrhythm sounds. Further rhythm sounds from the rhythm section progressregardless of musical sounds from the organ section, presenting greatdifficulties in stopping or terminating sounds from both sections at thesame time. Therefore a keyboard electronic musical instrumentprovided'with a conventional automatic rhythm instrument hasthe'drawback that where a beginner desires to practise a performance onthe organ section together with the automatic rhythm performance phraseby phrase or measure by measure, the rhythm performarice goes aheadfreely even when the player stops the performance on the organ sectionto repeat the exercising phrase or measure. Therefore such keyboardinstrument fails to be put to such practical application.

lt is accordingly the object of this invention to provide an electronicmusical instrument incorporated with an automatic rhythm device whichenables the tempo of the automatic rhythm performance to better meet thetempo of the organ section performance even though the organ section isplayed a little irregularly according to the players emotion and whichis also convenient for beginners to exercise intermittently andrepeatedly.

SUMMARY OF THE INVENTION An electronic musical instrument according to apreferred embodiment of this invention comprises an organ sectionincluding playing keys for producing or dinary melody sounds or chordsounds upon selective depression of the keys on the manual keyboard andbass sounds upon selective depression of the keys on the pedal keyboard;and an automatic rhythm section including a clock pulse oscillator forgenerating repetitive clock pulse corresponding to the shortest beatunit of rhythm performance and followed by four stages of binarycounters, a rhythm pattern pulse encoder for producing various sets ofrhythm pattern pulse trains by properly combining output pulses from thecounter stages, rhythm selector switches connected to the output side ofthe encoder and selecting out necessary pattern pulses, a plurality ofrhythm tone generators selectively triggered by the selected rhythmpattern pulse trains from the slector switches, a key depressiondetector associated with the playing keys and generating a trigger pulseupon depression of the keys, a rhythm cycle end detector connected tothe counter and generating another trigger pulse upon detection of theend of the counter cycle, and a start-stop control circuit connected tothe key depression detector and the cycle end detector for receiving thetrigger pulses and to the clock pulse oscillator for starting andstopping the oscillator according to the trigger pulses. The clock pulseoscillator included in the rhythm section is normally kept inoperativeby the action of the start-stop control circuit, and becomes operativewhen a trigger signal is generated by the first depression of the manualand/or pedal keys of the organ section which flips the control circuit,thereby initiating the automatic rhythm performance. When the automaticrhythm performance comes to the end of its pattern cycle, a pulse signalindicating the end of the pattern flips the control circuit to itsoriginal state, thereby stopping the clock oscillator to terminate theautomatic rhythm performance.

An electronic musical instrument according to this invention arranged asdescribed above'enables an automatic rhythm performance to be newlyinitiated by the play on the keyboard cycle by cycle, whereby the rhythmprogression is kept in tempo with the organ progression.

The present invention can be more fully understood from the followingdetailed description when taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic block circuit diagram of an electronic musicalinstrument according to an embodiment of this invention;

' FIG. 2 is a schematic block circuit diagram of a modification of FIG.1;

HO. 3 is a practical circuit arrangement of a clock oscillator includedin FIGS. 1 and 2;

FIG. 4 is a practical circuit arrangement of any of the binary countersincluded in FIGS. 1 and 2;

FIG. 5 is a practical circuit arrangement of the resetting circuit ofFlGS. l and 2; and

FIG. 6 is a practical circuit arrangement of the key depressiondetector, the start-stop control circuit and the rhythm cycle enddetector, in combination.

An electronic musical instrument according to the preferred embodimentof this invention comprises an organ section including playing keys 1, 2and a rhythm section including conventional portion 10 and a new portion20 each arranged as described below. As in an ordinary rhythminstrument, the rhythm section includes a clock pulse oscillator 11 of afree-running oscillation type such as an astable multivibrator whichgenerates a repetitive basic tempo pulse train having a frequencycorresponding to the shortest beat unit (e.g. a quaver or semiquaver) ofthe rhythm performance, the clock pulse oscillator 11 being providedwith a frequency changing elements 12 consisting of, for example, avariable resistor; a multistage frequency dividing counter chain 13formed of four stage cascade arranged binary circuits 13,, 13 13,, and13, and coupled with the clock pulse oscillator 11; a rhythm patternpulse encoder l4 constructed of the known diode matrix circuit (as setforth in the US. Pat. No. 3,358,068) including a plurality of columnlines L,, L L,, and row lines L,,, L,,, L,, and diodes D selectivelyconnected to the intersections of said column and row lines, so as tocomplete various sets of required rhythm pattern pulse trains; a rhythmselection circuit 15 allowing a player to select for performance thedesired one or more of the various sets or rhythm pattern pulse trainsconducted from the encoder l4; and a plurality of rhythm tone generatorsR,, R R,, for producing the preset one or more of the sounds like thosederived from various percussion instruments (e. g. snare drums, bassdrums and congas), ordinary chord or bass sounds or combinations thereofin response to the rhythm pattern pulses preselected by the rhythmselection circuit 15. Rhythm tone signals thus produced from the rhythmtone generators R, to R,, are conducted to a loud-speaker 17 through acommon amplifier 16. I

An electronic musical instrument according to this invention caninitiate the rhythm performance by the rhythm section 10 insynchronization with the start of the musical performance on the organsection and automatically terminate the rhythm performance at the end ofeach cycle. The newly added portion 20 includes a plurality of pedal keyswitches 21 associated with the pedal keys 1 and closed upon selectivedepression of the keys on the pedal keyboard for regular bassperformance, a plurality of manual key switches 22 closed upon selectivedepression of the keys on the manual keyboard for regular melody orchord performance, a start-stop control circuit 26, a rhythm cycle enddetector 27, and a normally open switch. The pedal and manual keyswitches 2l'and 22 are connected toa key depression detector through thecorresponding normal open switches 23 and 24 selectively closed by aplayer prior to performance. The key depression detector 25 is designedto produce a trigger pulse signal where the pedal and/or manual keys areselectively depressed. The above-mentionedtrigger signal is supplied asa set signal to the start-stop control circuit 26, thereby rendering theclock pulse oscillator 11 operative. Accordingly, a performance isalways effected under the condition where the rhythm sounds from therhythm section start with the musical sounds from the organ section. Thecycle end detector 27 is intended to detect the end of the one cycleoperating period of the binary circuits 13, to 13,, that is, the end ofarhythm pattern cycle defined by the period in which sixteen repetitivebasic tempo pulses from the clock pulse oscillator 11 are counted. Anoutput trigger signal from the detector 27 is supplied as a reset signalto the control circuit 26 if the normally open switch 28 is closed by aplayer prior to performance, thereby stopping the clock pulse oscillator11. Where the switch 28 is kept closed, the rhythm performance stops atthe end of the rhythm cycle and starts in time with organ key depressionagain. Where the switch 28 is kept open, the rhythm performance runsfreely as in the case of an ordinary automatic rhythm instrument, untilstopped by closure of gang-operated manual start-stop switches 29 and30.

The clock pulse oscillator 11 remains inoperative by the closed switch29 while the rhythm sounds are not to be played, and becomes operativeby opening of the switch 29 when the rhythm performance is to beconducted. When the rhythm performance is to be at rest, the binarycounters 13, to 13, are being reset to the orginal state by a resettingcircuit 31 under the control of the switch 30 interlocking with theswitch 29 (now both closed). Reference numeral 32 in FIG. 1 denotes afeedback switch provided, if required. When this switch 32 is closed,the first and second stage binary circuits 13, and 13 jointly act as aternary circuit, thereby changingthe rhythm pattern cycle from the 4-beat kind based on the period in which the clock pulse oscillatorproduces sixteen clock pulses in a cycle to the 3-beat kind based on theperiod in which twelve clock pulses are generated in a cycle.

FIG. 2 is a schematic circuit diagram of a modification of FIG. 1. Inthe embodiment of FIG. 1, the end of each rhythm pattern cycle wasdetected by an output signal from the counter chain 13. In themodification of FIG. 2, however, there is provided between the outputterminal of the clock pulse oscillator 11 (i.e. the input of thecounter) and the input terminal of the rhythm cycle end detector 27 aring counter 41 having the same unit operating period as that of thecounter chain 13, namely, sixteen (or twelve interchangeably) positionsto count sixteen (twelve) clock pulses generated by the clock pulseoscillator 11. Obviously, the modification of FIG. 2 can be operated inthe same manner and with the same effect as the embodiment of FIG. 1.

FIG. 3 shows a practical circuit arrangement of the clock pulseoscillator 11. A circuit 111 has two NPN transistor TR, and TR theemitters of which are connected to a grounded negative power source 51,and the collectors of which are connected to a positive power source 52via resistors R, and R The base of the transistor TR, is connected tothe collector of the transistor TR via a capacitor C, and also to thepositive power source 52 via the series circuit of a resistor R,, andthe variable resistor 12. The base of the transistor TR is connected tothe collector of the transistor TR, via a capacitor C and also to thepositive power source 52 via a resistor R The collector of thetransistor TR, is connected via a diode D, of the indicated polarity tothe collector of a transistor TR, included in a circuit 26 hereinaftershown in FIG. 6. The collector of the transistor TR, is connected to thetrigger point of the first stage binary counter 13, as hereinafter shownin FIG. 4. The circuit 111 arranged as described above acts as the knowastable multivibrator, and continuously produces from the collector ofthe transistor TR clock pulse trains having a frequency ortime widthdefined by the values of the capacitances and the resistances.

FIG. 4 is a practical circuit diagram of a given one of, the binarycounters 13, to 13,. A circuit 13'l has two N PN transistors TR 1 1 andTR The emitter of the transistor TR is connected to the collector of atransistor TR included in the resetting circuit 311 of FIG. 5 via a line61, and the emitter of the transistor TR is connected to the negativepower source 51. The collectors of both transistors TR and TR areconnected to the positive power source 52 via resistors R and R The baseof the transistor TR is connected to the collector of the transistor TRvia a parallel circuit of a capacitor C and a resistor R The base of thetransistor TR is connected to the collector of the transistor TR viaparallel connected capacitor C and resistor R Across the collectors ofboth transistors TR and TR is connected a series circuit of two couplingcapacitors C and C The common junction 62 of both capacitors C and C issupplied with output pulses acting as a trigger signal from the clockpulse oscillator or a binary circuit immediately preceding the aforesaidgiven binary circuit. The circuit 131 acts as the known bistablemultivibrator or flip-flop circuit. Under the reset condition of thecircuit 131, the transistor TR is on and the transistor TR is off, andunder the released condition the transistors TR and TR are alternatelyturned on and off receiving pulses from the preceding circuit.

FIG. 5 is a practical arrangement of the resetting circuit. This circuit311 includes two NPN transistors "PR and T11 their emitters areconnected to the negative power source 51 and their collectors areconnected to the positive power source 52 via resistors R and R The baseof the transistor TR- is connected to the collector of the transistor TRvia a resistor R and the base of the transistor TR is connected to thecollector of the transistor TR via a capacitor C and also to thepositive power source 52 via a resistor R Between the positive powersource 52 and the base of the transistor TR is connected via the switch30 a differentiation circuit 71 constructed of a grounded resistor R anda capacitor C the circuit 71 acting as a momentary trigger path as laterdescribed. Further if required, a series circuit of a capacitor C and aresistor R is disposed across the positive and negative power sources 52and 51, and also a forward connected diode D is provided between thebase of the transistor TR and the common connection 72 to the capacitorC and the resistor R The circuit 311 of the aforementioned arrangementacts as the known one-shot multivibrator. While the rhythm performanceis running, namely, while the switch 30 is opened, the transistor TR, iskept condutive and the transistor TR is kept conductive. Accordingly,the line 61 of FIG. 4 is grounded through the conducting transistor TRbringing the counters ready for counting operation.

- Each time the clock pulses are supplied to the counter,

the four-stage binary circuits 13 to 13, (only one indicated in FIG. 4)count down the pulses into halves successively. On the other hand, themoment the player closes the switch 30 to stop the rhythm sounds, thedifferentiation circuit 71 generates a differentiated positive goingimpulse which is applied as a trigger signal to the base of thetransistor TR to bring the transistor T11 conductive and consequentlythe transistor TR nonconductive. Therefore, the line 61 of FIG. 4 isbrought to the potential of the positive power source 52. Thus thebinary counters are forcefully reset regardless of its condition at thattime, becoming ready for the next new performance initiating from thefirst beat of the rhythm cycle. And after a length of time defined by atime constant derived from the product of the capacitance of thecapacitor C and the resistance of the resistor R the transistors TR, andTR have the condition reversed, namely, the transistor TR is turned onand the transistor TR is turned off, coming back to the normal state.

The capacitor C and resistor R are provided to cause the base of thetransistor TR to be momentarily supplied with a positive potentialthrough the diode D at the first power switching-on of the instrumentand to be released from such positive supply at the normal workingstate.

FIG. 6 shows a practical circuitry including the key depression detector25, the start-stop control circuit 26 and the rhythm cycle end detector27. The key depression detector 25 comprises a differentiation circuit251 formed of a capacitor C and a resistor R A forward polarized diode Dis connected parallel to the resistor R .to attain a DC. clamping toground. The rhythm cycle end detector 27 includes two directly coupledNPN transistors TR, and TR the emitters of which are connected to thenegative power source 51, and the collectors of which are connected tothe positive power source 52 via resistors R and R The base of thetransistor TR is connected to the output line of the final stage binarycounter 13, as shown in FIG. 4,'and the base of the transistor TR isconnected to the collector of the transistor TR The collector of thetransistor TR is connected via a capacitor C, to an output line 81 ofthe detector 27. Between the output line 81 and the positive powersource 52 is connected the diode D of the indicated polarlity to attaina DC. clamping to the positive power potential.

Thestart-stop control circuit 26 includes two NPN transistors TR and TRthe emitters of which are connected to the negative power source 51, andthe collectors of which are connected to the positive power source 52via resistors R and R The base of the transistor T12 is connected to thecollector of the transistor TR via a parallel circuit of a capacitor Cand resistor R Similarly, the base of the transistor TR is connected tothe collector of the transistor TR via a parallel circuit of a capacitorC and resistor R and, if required, also to the negative power source 51via a resistor R of a large resistance. The collector of the transistorTR, is connected to the output line 82 of the key depression detector251. The collector of the transistor TR is connected to the output line81 of the rhythm cycle end detector 27 via the switch 28 and also to thenegative power source 51 via the switch 29, and further to the collectorof the transistor TR included in the clock pulse oscillator 111 of FIG.3 via the diode D Obviously. the circuit 26 of FIG. 6 arranged asdescribed above act as a bistable circuit.

There will now be described the operation of the circuitry of FIG. 6.When the rhythm performance is set at rest, the switch 29 is closed andtherefore in the start-stop control circuit 26, the collector-emitterpath of transistor TR is shunted and transistor TR is kept in acondition ready to pass current. The transistor TR. is kept in a currentblocking condition in the rhythm cycle end detector 27, the transistorTR is kept in a current blocking condition being supplied with groundpotential from the transistor TR in FIG. 4, and the transistor TR iskept in a condition to pass current. Since, in this case, the switch-29is closed, the

collector of the transistor TR, included in the clock pulse oscillatorof FIG. 3 is connected to the grounded negative powersource 51 throughthe now forward biased diode D causing the collector-emitter path of thetransistor TR to be short-circuited. Accordingly, the clock pulseoscillator 111 is kept inoperative to prevent the generation of rhythmsounds.

For performance, a player opens the gang-actuated switches 29 and 30 andcloses one or both of the switches 23 and 24 as a preparation forautomatic performance, and then starts playing on the organ byselectively depressing the manual and and/or pedal keys. Under sucharrangement, desired musical sounds consisting of either melody soundsor chord and bass sounds or combinations thereof are produced from theorgan section. On the other hand, the moment the first one or ones ofthe pedal and/or manual keys are depressed and the associated keyswitches 21 and/or 22 are closed, a negative going voltage e as shown inFIG. 6 is generated. The signal e, is applied to the differentiationcircuit 251. A negative going impulse is produced at the falling of thesignal e and a positive going impulse at the rising thereof. Since thepositive impulse is shunted by the forward biased diode D the outputline 82 only produces the negative impulse e which is applied as atrigger signal to the collector of the transistor TR, included in thestart-stop control circuit 26, causing the collector-emitter path of thetransistor TR to be short-circuited. Accordingly, the other transistorTR, included in the control circuit 26 is rendered nonconductive and thetransistor TR, is rendered conductive. At this time, the diode D isbiased backward to release the clock pulse oscillator 111 of FIG. 3 fromits dormant state, causing the rhythm section automatically to producerhythm sounds. The base of the transistor TR still remains at the groundpotential. When the rhythm progression goes as far as a half of thecycle, the last counter stage 13, is flipped and the input to thetransistor TR exhibits a positive rise as shown by the waveform e In thedetector 27, therefore, the transistor TR, is turned on and thetransistor TR is turned off at the rising of the pulse e At this time,the capacitor C, connected to the collector of the transistor TR passesa positive pulse wave, which, however, is shunted to the power line 52through the now forward biased diode D and consequently does not appearon the output line '81 of the rhythm cycle and detector 27. As therhythm progression goes ahead further and comes as far as to the end ofthe rhythm cycle, the last counter stage 13, is flipped back and theinput to the transistor TR exhibits a negative going fall as shown bythe waveform e In the detector 27, therefore, the transistor TR isturned off and the transistor TR is turned on at the falling of thepulse e At this time, the capacitor C passes a negative pulse wave e,,which backward biases the diode D and is conducted to the output line 81of said detector 27, and then comes out as a trigger signal to thecollector of the transistor TR, included in the start-stop controlcircuit 26, causing the collector-emitter path of the transistor TR, tobe short-circuited. Accordingly, the other transistor TR of the controlcircuit 26 is turned off, and the transistor TR is turned on, which inturn shunts the collector and emitter of the transistor TR through theforward biased diode D,. Thus the clock pulse oscillator 111 is againbrought to its stopped to cease the rhythm per formance. With the switch28 opened, the rhythm cycle end detector 27 does not flip the start-stopcontrol circuit, so that the rhythm section 10 obviously continues theautomatic rhythm performance as on the conventional automatic rhythminstrument.

What is claimed is:

1. An electronic musical instrument comprising an organ section forplaying melody and accompaniment tones and including a plurality ofplaying keys; and an automatic rhythm section including a clock pulseoscillator generating repetitive clock pulses, counters connected tosaid clock pulse oscillator for counting down to submultiples of thefrequency of said clock pulses from said clock pulse oscillator, arhythm pattern pulse encoder connected to said counters for producingplural sets of rhythm pattern pulse trains, each rhythm pattern pulsetrain being comprised of a combination of different preset output pulsesfrom said counters, a rhythm selection circuit coupled with said encoderto select the desired one or more of the various rhythm pattern pulsetrains from said encoder, and a plurality of rhythm tone generatorsconnected to said selection circuit and being selectively triggered bythe rhythm pattern pulse train preselected by said rhythm selectioncircuit to produce said preset one or more rhythm sounds in exact timingwith the tempo of the preselected rhythm pattern,

the improvement comprising:

a key depression detector coupled to the said playing keys andgenerating a trigger pulse upon depression of said keys,

a rhythm cycle end detector connected to at least one of said countersand generating another trigger pulse upon detection of the end of thecounter cycle, and

a start-stop control circuit having inputs coupled to said keydepression detector and to said rhythm cycle end detector for receivingsaid trigger pulses and having an output coupled to said clock pulseoscillator for generating a first output signal for normally maintainingsaid clock pulse oscillator inoperative, said start-stop control circuitincluding means responsive to the trigger signal from said keydepression detector for generating a second output signal to render saidclock pulse oscillator operative upon receipt of the trigger signal fromsaid key depression detector, and means responsive to the trigger signalfrom said rhythm cycle end detector for generating said first outputsignal to render said clock pulse oscillator inoperative upon receipt ofthe trigger signal from said rhythm cycle end detector, therebyautomatically ending rhythm performance at the end of each rhythm cycle.

2. An electronic musical instrument claimed in claim 1 wherein saidstart-stop control circuit comprises a flip-flop circuit.

3. An electronic musical instrument claimed in claim 1 further includinga resetting circuit coupled to said counters for resetting said countersback to a preset original state prior to rhythm performance.

4 An electronic musical instrument claimed in claim 3 wherein saidresetting circuit comprises a one shot multivibrator.

5. An electronic musical instrument claimed in claim 1 wherein saidclock pulse oscillator comprises an astable multivibrator with afrequency control element.

lator generating repetitive clock pulses, counters connected to saidclock pulse oscillator for counting down to submultiples of thefrequency of said clock pulses from said clock pulse oscillator, arhythm pattern pulse encoder connected to said counters for producingplural sets of rhythm pattern pulse trains, each rhythm pattern pulsetrain being comprised of a combinaton of different preset output pulsesfrom said counters, a rhythm selection circuit coupled with said encoderto v select the desired one or more of the various rhythm pattern pulsetrains from said encoder, and a plurality of rhythm tone generatorsconnected to said selection circuit and being selectively triggered bythe rhythm pattern pulse train preselected by said rhythm selectioncircuit to produce said preset one or more rhythm sounds in exact timingwith the tempo of the preselected rhythm pattern,

the improvement comprising:

a key depression detector coupled to the plain keys and generating atrigger pulse upon depression of said keys,

a ring counter coupled to the input of said counters and producing asignal at the end of a cycle,

a rhythm cycle end detector connected to the output of said ring counterand generating another trigger pulse upon detection of the end of thering counter cycle, and

a start-stop control circuit having inputs coupled to said keydepression detector and to said rhythm cycle end detector for receivingsaid trigger pulses and having an output coupled to said clock pulseoscillator for generating a first output signal for normally maintainingsaid clock pulse oscillator inoperative, said s'tart-stop controlcircuit including means responsive to the trigger signal from said keydepression detector for generating a second output signal to render saidclock pulse oscillator operative upon receipt of the trigger signal fromsaid key depression detector, and means responsive to the trigger signalfrom said rhythm cycle end detector for generating said first outputsignal to render said clock pulse oscillator inoperative upon receipt ofthe trigger signal from said rhythm cycle end detector, therebyautomatically ending rhythm performance at the end of each rhythm cycle.

9. An electronic musical instrument claimed in claim 9 wherein saidstart-stop control circuit comprises a flip-flop circuit.

10. An electronic musical instrument claimed in claim 9 wherein saidclock pulse oscillator ccomprises an astable multivibrator with afrequency control element.

1. An electronic musical instrument comprising an organ section forplaying melody and accompaniment tones and including a pLurality ofplaying keys; and an automatic rhythm section including a clock pulseoscillator generating repetitive clock pulses, counters connected tosaid clock pulse oscillator for counting down to submultiples of thefrequency of said clock pulses from said clock pulse oscillator, arhythm pattern pulse encoder connected to said counters for producingplural sets of rhythm pattern pulse trains, each rhythm pattern pulsetrain being comprised of a combination of different preset output pulsesfrom said counters, a rhythm selection circuit coupled with said encoderto select the desired one or more of the various rhythm pattern pulsetrains from said encoder, and a plurality of rhythm tone generatorsconnected to said selection circuit and being selectively triggered bythe rhythm pattern pulse train preselected by said rhythm selectioncircuit to produce said preset one or more rhythm sounds in exact timingwith the tempo of the preselected rhythm pattern, the improvementcomprising: a key depression detector coupled to the said playing keysand generating a trigger pulse upon depression of said keys, a rhythmcycle end detector connected to at least one of said counters andgenerating another trigger pulse upon detection of the end of thecounter cycle, and a start-stop control circuit having inputs coupled tosaid key depression detector and to said rhythm cycle end detector forreceiving said trigger pulses and having an output coupled to said clockpulse oscillator for generating a first output signal for normallymaintaining said clock pulse oscillator inoperative, said start-stopcontrol circuit including means responsive to the trigger signal fromsaid key depression detector for generating a second output signal torender said clock pulse oscillator operative upon receipt of the triggersignal from said key depression detector, and means responsive to thetrigger signal from said rhythm cycle end detector for generating saidfirst output signal to render said clock pulse oscillator inoperativeupon receipt of the trigger signal from said rhythm cycle end detector,thereby automatically ending rhythm performance at the end of eachrhythm cycle.
 2. An electronic musical instrument claimed in claim 1wherein said start-stop control circuit comprises a flip-flop circuit.3. An electronic musical instrument claimed in claim 1 further includinga resetting circuit coupled to said counters for resetting said countersback to a preset original state prior to rhythm performance.
 4. Anelectronic musical instrument claimed in claim 3 wherein said resettingcircuit comprises a one shot multivibrator.
 5. An electronic musicalinstrument claimed in claim 1 wherein said clock pulse oscillatorcomprises an astable multivibrator with a frequency control element. 6.An electronic musical instrument claimed in claim 1 wherein saidcounters comprise four stage cascade arranged binary circuits.
 7. Anelectronic musical instrument claimed in claim 6 wherein the first andsecond stages of said binary circuit have a feedback loop which isselectively closed, and said first and second stage binary circuits withthe closed feedback loop constitute a single ternary circuit.
 8. Anelectronic musical instrument comprising an organ section for playingmelody and accompaniment tones and including a plurality of playingkeys; and an automatic rhythm section including a clock pulse oscillatorgenerating repetitive clock pulses, counters connected to said clockpulse oscillator for counting down to submultiples of the frequency ofsaid clock pulses from said clock pulse oscillator, a rhythm patternpulse encoder connected to said counters for producing plural sets ofrhythm pattern pulse trains, each rhythm pattern pulse train beingcomprised of a combinaton of different preset output pulses from saidcounters, a rhythm selection circuit coupled with said encoder to selectthe desired one or more of the various rhythm pattern pulse trains fromsaid encoder, and a Plurality of rhythm tone generators connected tosaid selection circuit and being selectively triggered by the rhythmpattern pulse train preselected by said rhythm selection circuit toproduce said preset one or more rhythm sounds in exact timing with thetempo of the preselected rhythm pattern, the improvement comprising: akey depression detector coupled to the playing keys and generating atrigger pulse upon depression of said keys, a ring counter coupled tothe input of said counters and producing a signal at the end of a cycle,a rhythm cycle end detector connected to the output of said ring counterand generating another trigger pulse upon detection of the end of thering counter cycle, and a start-stop control circuit having inputscoupled to said key depression detector and to said rhythm cycle enddetector for receiving said trigger pulses and having an output coupledto said clock pulse oscillator for generating a first output signal fornormally maintaining said clock pulse oscillator inoperative, saidstart-stop control circuit including means responsive to the triggersignal from said key depression detector for generating a second outputsignal to render said clock pulse oscillator operative upon receipt ofthe trigger signal from said key depression detector, and meansresponsive to the trigger signal from said rhythm cycle end detector forgenerating said first output signal to render said clock pulseoscillator inoperative upon receipt of the trigger signal from saidrhythm cycle end detector, thereby automatically ending rhythmperformance at the end of each rhythm cycle.
 9. An electronic musicalinstrument claimed in claim 9 wherein said start-stop control circuitcomprises a flip-flop circuit.
 10. An electronic musical instrumentclaimed in claim 9 wherein said clock pulse oscillator comprises anastable multivibrator with a frequency control element.